On his first expedition, Zebulon Pike left St. Louis, Mo., and explored the Mississippi River as far as Leech Lake and Sandy Lake in Minnesota, and on his second expedition Pike traveled westward to explore the sources of the Red River and the Arkansas River, part of the territory of the newly-acquired Louisiana Purchase. Pike's Peak in Colorado, which he climbed partway, is named after him.
In August 1805, General James Wilkinson, commander of the United States Army, sent Pike up the Mississippi with the task of discovering its headwaters. Pike, then a lieutenant, led twenty men into Minnesota. They spent the winter there and signed a treaty with the Sioux Indians, but they failed to find the river's source.
Wilkinson sent Pike out from St. Louis again in July of 1806. This time he traveled as far as present-day Pueblo, Co., where he explored the mountains and tried to climb Pike's Peak. Afterwards he turned south, and he and his men built a small fort on the shores of the Rio Grande River. As this was then Spanish territory, they were apprehended by Spanish soldiers, who took them first into Mexico before returning them to the United States.
By then, General Wilkinson had been implicated with Aaron Burr in a conspiracy to create a separate nation in the southwest. Pike was briefly suspected of being involved but then cleared. He was later promoted to major and then to general. He died leading an American attack on York, now Toronto in Canada, in 1813.